Abstract
We here report the observation of an adult Masked Booby Sula dactylatra , which was made off Sado Island in the Japan Sea (N38˚06'10'', E138˚33'56''–N38˚04'20'', E138˚40'10'') on September, 14, 2011. This bird flew above the ocean, making some dives into the water for foraging, and floating on the water surface during 0955–1010 h of that day. The Masked Booby is rarely recorded in and around the Japan Sea. The species' nearest breeding site, which has been known to be active recently, is Nishinoshima Island of the Ogasawara Islands, approximately 1,200 km to the south of the location of observation.
